#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
class Solution {
public:
    void reverseString(vector<char>& s) {
        int left = 0, right = s.size() - 1;
        while (left < right) {
            swap(s[left], s[right]);
            left++, right--;
        }
        return;
    }
};